Under the terms of the deal, BT Vision will become the exclusive home of European events featuring Premiership clubs from the 2014/15 season.

However, Sky Sports announced a separate deal on the same day with the ERC, which was claimed to give the satellite broadcaster rights to exclusive coverage of European club rugby from 2014/15.

Both bodies claim that the other does not have the power to sell the rights.

Speaking to BBC News, an ERC spokesman said that Premiership Rugby's European deal with BT is "in breach both of International Rugby Board regulations and of a mandate from the ERC Board itself".

They added: "European club rugby's six participant unions have granted the authority to sell broadcast rights to its tournaments solely to ERC.

"It was unanimously agreed at an ERC Board meeting on June 6, 2012, that ERC would conclude a new four-year agreement with Sky Sports. Premiership Rugby was party to that decision."

However, Premiership Rugby counters that ERC's rights to sell broadcast deals on behalf of the unions runs out in 2014, meaning it can sell the rights to BT from that point.

In its own statement, the body said: "On July 27, 2012, ERC was reminded of this in writing, and this was copied to Sky Sports.

"We also note ERC's reference to its board meeting on 6 June, 2012. No specific broadcast deal was presented or voted on at this or any subsequent ERC board meeting. In any case any such deal could not have included matches involving Premiership Rugby clubs.

"ERC's suggestion that Premiership Rugby may be in breach of IRB regulations is wrong."